Heretofore, the so-called AEM (Articulation Element Modeling) technique has been known as a technique for facilitating realistic reproduction and reproduction control of various rendition styles (or various types of articulation) to natural musical instruments, and it has been conventional to synthesize high-quality tone waveforms using the AEM technique. As known in the art, the AEM technique can generate a continuous tone waveform with high quality by time-serially combining a plurality of ones of rendition style modules corresponding to various portions of tones, such as head-type or head-portion rendition style modules each representative of a rise (i.e., head or attack) portion of a tone, body-portion rendition style modules each representative of a steady portion (or body portion) of a tone, tail-portion modules each representative of a fall (i.e., tail or release) portion and joint-portion rendition style modules each representative of a connecting portion or joint portion for continuously connecting between successive notes (or note portions) with no break of tone therebetween using a desired rendition style like a legato rendition style. One example of tone synthesis using the AEM technique is disclosed in Japanese Patent Application Laid-open Publication No. 2002-287759. Note that, throughout this specification, the terms “tone waveform” are used to mean a waveform of a voice or any desired sound rather than being limited only to a waveform of a musical tone. Further, in each joint-portion rendition style module, waveform data of a former-half module portion where a tone pitch of a first (i.e., preceding) note can be heard mainly as compared to a tone pitch of a second (i.e., succeeding) note will hereinafter be referred to as “pre-note portion”, and waveform data a latter-half module portion following the former-half module portion (i.e., module portion following a predetermined shift point where a human player starts to auditorily perceive that sounding of the succeeding note has started with a shift from the tone pitch of the preceding note to the tone pitch of the succeeding note) will hereinafter be referred to as “post-note portion”.
In synthesis of a connecting tone of a joint portion using the above-mentioned joint-portion rendition style module in a real-time performance where tones are sequentially synthesized in response to performance operation by a human player, there may sometimes be caused an auditory tone-generating delay (also called “latency”) from a note-on instruction of a succeeding note to a time point when sounding of the succeeding note can start to be heard. This is, for example, due to some characteristics specific to the joint-type or joint-portion rendition style module that (1) a considerable time is required for operations to permit a smooth tone pitch connection and shift from the currently-sounded preceding note to the succeeding note to be sounded next, such as operations for adjusting a tone pitch, amplification, etc. of the joint-portion rendition style module in accordance with respective rendition style modules of the adjoining preceding and succeeding notes and (2) the time required for the tone pitch shift from the currently-sounded preceding note to the succeeding note (i.e., this time corresponds to a time length from the start of synthesis of a tone of the pre-note portion to the start of synthesis of a tone of the post-note portion) depends on the tone pitch of the preceding note, type of a musical instrument, performance style, etc. Thus, even where the human player wants to execute a performance with priority given to tone generation timing of the succeeding note (i.e., without causing a latency) at the sacrifice of tone quality, it has heretofore been difficult to execute such a performance due to the characteristics specific to the joint-portion rendition style module. As an alternative approach, it is conceivable to synthesize a tone using a tail-portion rendition style module for the preceding note and a head-portion rendition style module for the succeeding note without using a joint-portion rendition style module. With such an alternative approach, however, a feeling of connection between the preceding and succeeding notes would be undesirably lost. Thus, there has been a demand for an improved technique, which in a case where a tone of a joint portion for connecting between adjoining or successive notes is to be synthesized, not only can synthesize a tone with the tone quality given priority over the tone generation timing of the succeeding note as in the past but also can synthesize a tone with the tone generation timing of the succeeding note given priority over the tone quality, and which can synthesize a tone with minimized degradation of the tone quality even in the case where priority is given to the tone generation timing. But, to date, no such technique has been proposed or developed.